At this time it is difficult to identify any reason, other than insufficient directed effort, for the present lack of a nonhuman primate model of in vitro fertilization and reimplantation. The proposed research is designed to provide conclusive evidence of in vitro fertilization in the squirrel monkey and chimpanzee. Subsequent to demonstration of fertilization by the acceptable criteria of sperm penetration, pronucleus formation, cleavage, and karyotyping, conditions will be sought for successful reimplantation and development of nonhuman primate ova. Gametes will be recovered surgically, at laparotomy or laparoscopy, and depending on the specific experiment hormonal pretreatment will be used to increase the yield of oocytes, or a rapid assay for LH will be used to time the recovery of the single oocyte destined to ovulate in a given cycle. Semen will be obtained by electroejaculation or masturbation. Recent success with in vitro fertilization and reimplantation of human gametes has raised several ethical and scientific questions. Further development of the technique to attain its potential in reducing the incidence of human fetal abnormality, as well as providing a model for extended study of teratogenesis, trisomy and effect of aging on primate gametes will be contingent on adequate background research using nonhuman material. The priority objective of this work is to establish nonhuman primate models of fertilization in vitro, and the proposed effort could be justified solely within that context. Additional research is proposed for development and application of the model so that maximum benefit can be derived from the grant during its proposed duration.